Paul Romatschke talks with
ScienceWatch.com and answers a few questions about
this month's New Hot Paper in the field of
Article Title: Viscosity information from
relativistic nuclear collisions: How perfect is the fluid
observed at RHIC?
Journal: PHYS REV LETT
Year: no.-172301 OCT 26 2007
* Univ Washington, Inst Nucl Theory, Box 351550, Seattle,
WA 98195 USA.
* Univ Washington, Inst Nucl Theory, Seattle, WA 98195
(addresses have been truncated)
Why do you think your paper is highly
The value of the viscosity of hot nuclear matter has been widely discussed
in the high energy physics community. Our article showed how to extract
information about this quantity from experimental data and provided
estimates for the value of the viscosity.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
"The value of the viscosity of hot
nuclear matter has been widely discussed in
the high energy physics
It describes a new method (viscous hydrodynamic simulations with fluid
velocities very close to the speed of light) and applies this method to
constrain an unknown quantity using a synthesis of existing knowledge.
Would you summarize the significance of your paper
in layman's terms?
Loosely speaking, a smaller value of viscosity means that a fluid flows
more like water than honey, and our results suggest that hot nuclear matter
has the smallest viscosity of any known fluid studied in the laboratory. It
is less viscous than even
How did you become involved in this research, and
were there any problems along the way?
Fluid dynamics is a fascinating theoretical tool: it is comparatively
simple and universal in describing very different physical systems, ranging
from the weather on our planet to the behavior of hot nuclear matter.
The theory of viscous fluids with velocities close to the speed of light
was not sufficiently developed when we started our work, which was a
problem we could overcome by drawing on recent advances in high energy
physics. However, the biggest problem was psychological: colleagues were
warning us about all the numerical challenges we would face, recommending
we should tackle simpler problems. Luckily, we ignored those warnings.
Where do you see your research leading in the
Further refinements of our method and/or new ideas are needed to extract
the viscosity of nuclear matter, including its error bar. Our article was
only the first step in this direction.
Do you foresee any social or political implications
for your research?
No. However, implications from basic science are often unpredictable. For
example, on December 8, 1864, James Clerk Maxwell outlined the theory of
electromagnetism in a presentation to the Royal Society—without which
there would be no cell phones today—in his paper: "A Dynamical Theory
of the Electromagnetic Field," Philosophical Transactions of the Royal
Society of London 155: 459-512, 1865.
Paul Romatschke, Ph.D.
Research Assistant Professor
Institute for Nuclear Theory (INT)
Department of Physics
University of Washington
Seattle, WA, USA Web ¦